Method of erecting a cantilever truss bridge; bridge; panel for a bridge; and dummy chords for panel

ABSTRACT

An improved method of erecting a cantilever truss bridge; an improved bridge; an improved panel for a bridge; and improved dummy chords for a panel are disclosed.

United States Patent 1191 11] 3,833,959 McGrath 1451 Sept. 10,1974

[54] METHOD OF ERECTING A CANTILEVER [56] References Cited TRUSS BRIDGE; BRIDGE; PANEL FOR A UNITED STATES PATENTS BRIDGE; AND DUMMY CHORDS FOR 384,197 6/1888 Duvai 14/13 PANEL 1,256,081 2/1918 Turner 1,56 1 l 1 Sh k 7. [75] Inventor: William K. McGratlli St. Clair Twp., 3 23 x33 ggfi i Allegheny County 1,967,828 7/1934 Leake [73] Assigneez United States Steel corporafion 3,062,340 11/ 1962 Hunnebeck, 14/13 X Pittsburgh, Pa. Primary ExammerN1le C. Byers, Jr. Filed: 1972 Attorney, Agent, or FirmDavid S. Urey [21] Appl. No.: 308,366

[57] ABSTRACT An improved method of erecting a cantilever truss C(i1 14/14, bridge; an improved bridge; an improved panel for a [58] Field of Search 14/3, 4, 5, 7, 13, 14, EF a mpmved dummy chmds a panel are 22 Claims, 13 Drawing Figures Predflermincd uac/wa-um/ "5""" "E 01112-013; mus-um; p( /3'-U/4'j Q 12 /3 11/4 (mam/3 11147 LIZ L/3 L/4 ls! Anchor Arm Cumi- Suspended Fred 1- LDC m 58 Clearance L 3) 2nd 2nd Suspended f 2 nd Anchor 4,111

Span ever PAIENTED' mm amasss sum 11: s

PATENTEBsEM 01914 253153.959

Horizontal docking Force at /8 PAIENIEDSEPIWH smwsse sum 5 or 6 Point METHOD The method of erecting a cantilever truss bridge having a first half provided with a first anchor arm mounted at one end on a first anchor point and the other end on a first pier, and a first cantilever arm secured to the other end of the first anchor arm and projecting inwardly therefrom from the first pier; and a second half provided with a second anchor arm mounted at one end on a second anchor point and on the other end on a second pier, and a second cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the second pier includes the steps of:

a. mounting first quadrilateral dummy panels on the first cantilever arm and including:

1. mounting a first pair of opposed top dummy chords on the other end of the first cantilever arm for providing a first top predetermined panel point to panel point length and restraining said first pair of opposed top dummy chords to prevent any change in the first top predetermined panel point to panel point length;

2. mounting a first pair of opposed bottom dummy chords on the other end of the first cantilever arm for providing a first bottom predetermined panel point to panel point length and restraining said first pair of opposed bottom dummy chords to prevent any decrease in the first bottom predetermined panel point to panel point length;

a. the first bottom predetermined panel point to panel point length being greater than the first top predetermined panel point to panel point length to compensate for the deflection of a first suspended span during erection thereof;

3. mounting a pair of diagonals between each of the first top dummy chords and each of the first bottom dummy chords for completing the first quadrilateral dummy panels;

b. adding a plurality of pairs of successive opposed portions of the first suspended span (including floor and bracing members of the first suspended span for rigidity) to each of the first quadrilateral dummy panels to complete the first suspended span so that:

l. a center vertical member of the first suspended span lies in a truly vertical plane;

c. mounting second quadrilateral dummy panels on the second cantilever arm and including:

1. mounting a second pair of opposed top dummy chords on the other end of the second cantilevered arm for providing a second top predetermined panel point to panel point length and restraining said second pair of opposed top dummy chords to prevent any change in the second top predetermined panel point to panel point length;

2. mounting a second pair of opposed bottom dummy chords on the other end of the second cantilevered arm for providing a second bottom predetermined panel point to panel point length and restraining said second pair of opposed bottom dummy chords to prevent any decrease in the second bottom predetermined panel point to panel point length; a

a. the second bottom predetermined panel point to panel point length being greater than the second top predetermined panel point to panel point length to compensate for the deflection of a second suspended span during erection thereof; and

3. mounting a pair of diagonals between each of the second top dummy chords and each of the second bottom dummy chords for completing the second quadrilateral dummy panels;

d. adding a plurality of pairs of successive opposed portions of said second suspended span, which is lighter in weight than the first suspended span (including floor and bracing members of the second suspended span for rigidity) to each of the second quadrilateral dummy panels to complete the second suspended span so that:

l. a line of action of the center vertical member of the second suspended span lies in a truely vertical plane and is spaced a predetermined clearance distance from the center vertical member of the first suspended span,

e. moving one half of the first half and the second half of the truss cantileveredbridge toward the other half of the first half and the second half so that the line of action of said second half registers with the center vertical member of said first half to permit closing of the truss cantilevered bridge;

f. securing the first half to the second half to close the truss cantilevered bridge;

g. swinging the bridge by simultaneously elevating the one end of the first anchor arm with respect to the first anchor point and the one of the second anchor arm with respect to the second anchor point to eliminate the erection stresses in the first top dummy chords and the first bottom dummy chords and the second top dummy chords and the second bottom dummy chords; and

h. releasing the restraint from the first top dummy chords and the first bottom dummy chords and the second top dummy chords and'the second bottom dummy chords so that the dummy chords will not carry direct stress thereby:

l. eliminating jacking in the dummy chords during closing and swinging of the bridge;

2. reducing the total jacking requirements for the erection of the bridge; and

3. avoiding the temporary removal of supports at the first anchor point and the second anchor point at any stage of the erection of the bridge.

TOP DUMMY CHORD For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier and a cantilever arm secured to the other end of the anchorarm and projecting inwardly therefrom from the first pier a top dummy chord is provided and has:

a. a dummy top chord mounted on the other end of the cantilever arm for providing a top predetermined panel point to panel point length;

b. gusset means for connecting the top dummy chord to the cantilever arm;

c. positioning means associated with the top dummy chord UDC and the gusset means for providing the top predetermined panel point to panel point length; and

d. restraining means on the gusset means for locking the positioning means to prevent any change in the top predetermined panel point to panel point length when the dummy top chord is tensioned by the addition thereto of a suspended span.

BOTTOM DUMMY CHORD For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the pier a bottom dummy chord is provided and has:

a. a bottom dummy chord mounted on the other end of the cantilever arm for providing a bottom predetermined panel point to panel point length;

b. gusset means for connecting the bottom dummy chord to the cantilever arm; and

c. spacing means disposed between the other end of the lower dummy chord and a suspended span;

1 the spacing means being adapted to maintain the bottom predetermined panel point to panel point length when the bottom dummy chord is compressed by the weight of the suspended span.

QUADRILATERAL DUMMY PANEL For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the pier, a quadrilateral panel is provided and has:

a. a quadrilateral dummy panel 22 is disclosed and is mounted on the cantilever arm and including:

1. a top dummy chord on the other end of the cantilever arm for providing a top predetermined panel point to panel point length;

2. restraining means associated with the cantilever arm and the top dummy chord for preventing any change in the top predetermined panel point to 4 panel point length;

3. a bottom dummy chord on the other end of the cantilever arm in spaced relation to the top dummy chord for providing a bottom predetermined panel point to panel point length;

4. spacing means associated with the other end of 5 the lower dummy chord and the suspended span to prevent any decrease in the bottom predetermined panel point to panel point length; and

5. a pair of diagonals between the top dummy chord and the bottom dummy chord to complete the quadrilateral dummy panel.

HALF BRIDGE l. a top dummy chord on the other end of the cantilever arm for providing a top predetennined panel point to panel point length;

2. restraining means associated with the cantilever arm and the top dummy chord for preventing any change in the top predetermined panel point to panel point length;

3. a bottom dummy chord on the other end of the cantilever arm in spaced relation to the top dummy chord for providing a bottom predetermined panel point to panel point length; and

4. spacing means associated with the other end of the lower dummy chord and the suspended span to prevent any decrease in the bottom predetermined panel point to panel point length; and

5. a pair of diagonals between the top dummy chord and the bottom dummy chord to complete the quadrilateral dummy panel.

BACKGROUND OF THE INVENTION Heretofore, truss cantilevered bridges have required jacking at truss chords for closing the span and have utilized large jacking requirements to perform this task.

I am aware of the following prior art:

US. Pat. No. Inventor Issued Class l,868,630 Dcvou 7/26/32 2,079,095 Wichcrt 10/4/37 14/4 3,027,633 Murphy 4/3/62 29/429 3,564,567 Mladycnovitch 2/ 1 6/71 29/429 OBJECTS OF THE INVENTION It is the general object of this invention to avoid and overcome the foregoing and other difficulties of and objections to prior art practices by the provision of an improved method of erecting a cantilevered truss bridge, improved bridge, improved panel for a bridge, and improved dummy chords for the panel which:

a. eliminate for any deflection of the first suspended span and the second suspended span as they are cantilevered from opposed first cantilevered arm and second cantilevered arm respectively;

b. eliminate jacking at truss chords; and

c. reduce the jacking requirement for closing the span to about one-fifth of that used in conventional methods.

BRIEF SUMMARY OF THE INVENTION The aforesaid objects of this invention, and other objects which will become apparent as the description proceeds, are achieved by providing:

A. an improved method of erecting a bridge;

B.,C. improved top and bottom dummy chords for a panel;

D. an improved dummy panel; and

E. an improved bridge.

METHOD The method of erecting a cantilever truss bridge having a first half provided with a first anchor arm mounted at one end on a first anchor point and the other end on a first pier, and a first cantilever arm secured to the other end of the first anchor arm and projecting inwardly therefrom from the first pier; and a second half provided with a second anchor arm mounted at one end on a second anchor point and on the other end on a second pier, and a second cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the second pier includes the steps of:

a. mounting first quadrilateral dummy panels on the first cantilever arm and including:

1. mounting a first pair of opposed top dummy chords on the other end of the first cantilever arm for providing a first top predetermined panel point to panel point length and restraining said first pair of opposed top dummy chords to prevent any change in the first top predetermined panel point to panel point length;

2. mounting a first pair of opposed bottom dummy chords on the other end of the first cantilever arm for providing a first bottom predetermined panel point to panel point length and restraining said first pair of opposed bottom dummy chords to prevent any decrease in the first bottom predetermined panel point to panel point length;

a. the first bottom predetermined panel point to panel point length being greater than the first top predetermined panel point to panel point length to compensate for the deflection of a first suspended span during erection thereof;

3. mounting a pair of diagonals between each of the first top dummy chords and each of the first bottom dummy chords for completing the first quadrilateral dummy panels;

b. adding a plurality of pairs of successive opposed portions of the first suspended span (including floor and bracing members of the first suspended span for rigidity) to each of the first quadrilateral dummy panel to complete the first suspended span so that:

l. a center vertical member of the first suspended span lies in a truly vertical plane;

c. mounting second quadrilateral dummy panels on the second cantilever arm and including:

1. mounting a first pair of opposed top dummy chords on the other end of the second cantilevered arm for providing a second top predetermined panel point to panel point length and restraining said first pair of opposed dummy chords to prevent any change in the second top predetermined panel point to panel point length;

2. mounting a second pair of opposed bottom dummy chords on the other end of the second cantilevered arm for providing a second bottom predetermined panel point to panel point length and restraining said second pair of opposed bottom dummy chords to prevent any decrease in the second bottom predetermined panel point to panel point length;

a. the second bottom predetermined panel point to panel point length being greater than the second top predetermined panel point to panel point length to compensate for the deflection of a secondsuspended span during erection thereof; and

3. mounting a pair of diagonals between each of the second top dummy chords and each of the second bottom dummy chords for completing the second quadrilateral dummy panels;

d. adding a plurality of pairs of successive opposed portions of said second suspended span, which is lighter in weight than the first suspended span (ineluding floor and bracing members of the second i suspended span for rigidity) to each of the second quadrilateral dummy panel to complete the second suspended span so that:

l. a line of action of the center vertical member of the second suspended span lies in a truly vertical plane and is spaced a predetennined clearance distance from the center vertical member of the first suspended span,

e. moving one half of the first half and the second half of the truss cantilevered bridge toward the other half of the first half and the second half so that the line of action of the second half registers with the center vertical member of the first half to permit closing of the truss cantilevered bridge;

f. securing the first half to the second half to close the truss cantilevered bridge;

g: swinging the bridge by simultaneously elevating the one end of the first anchor arm with respect to the rear anchor point and the one end of the second anchor arm with respect to the second rear anchor point to eliminate the erection stresses in the first top dummy chords and the first bottom dummy chords and the second top dummy chords and the second bottom dummy chords; and

h. releasing the restraint from the first top dummy chords and the first bottom dummy chords and the second top dummy chords and the second bottom dummy chords so that the dummy chords will not carry direct stress thereby:

1. eliminating jacking in the dummy chords during closing and swinging of the bridge;

2. reducing the total jacking requirements for the erection for the bridge; and

3. avoiding the temporary removal of supports at the first anchor point and the second anchor point at any stage of the erection of the bridge.

TOP DUMMY CHORD For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the first pier a top dummy chord is provided and has:

a. a dummy top chord mounted on the other end of the cantilever arm for providing a top predetermined panel point to panel point length;

b. gusset means for connecting the top dummy chord to the cantilever arm;

c. positioning means associated with the top dummy chord UDC and the gusset means for providing the top predetermined panel point to panel point length; and

d. restraining means on the gusset means for locking the positioning means to prevent any change in the top predetermined panel point to panel point length when the dummy top chord is tensioned by the addition thereto of a first suspended span.

BOTTOM DUMMY CHORD For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the pier a bottom dummy chord is provided and has:

a. a bottom dummy chord mounted on the other end of the cantilever arm for providing a bottom predetermined panel point to panel point length;

b. gusset means for connecting the bottom dummy chord to the cantilever arm; and

c. spacing means disposed between the other end of the lower dummy chord and a suspended span,

1. the spacing means being adapted to maintain the bottom predetermined panel point to panel point length when the bottom dummy chord is compressed by the weight of the suspended span.

QUADRILATERAL DUMMY PANEL For a half of a cantilever truss bridge provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier and a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the pier, a quadrilateral dummy panel is provided and has:

a. a quadrilateral dummy panel mounted on the cantilever arm and including:

1. a top dummy chord on the other end of the cantilever arm for providing a top predetermined panel point to panel point length;

2. restraining means associated with the cantilever arm and the top dummy chord for preventing any change in the top predetermined panel point to panel point length;

3. a bottom dummy chord on the other end of the cantilever arm in spaced relation to the top dummy chord for providing a bottom pedetermined panel point to panel point length;

4. spacing means associated with the other end of the lower dummy chord and the suspended span to prevent any decrease in the bottom predetermined panel point to panel point length; and

5. a pair of diagonals between the top dummy chord and the bottom dummy chord to complete the quadrilateral dummy panel.

HALF BRIDGE The combination is disclosed of: a. a half of a cantilever truss bridge having:

1. an anchor arm mounted at one end on an anchor point and at the other end om a pier;

2. a cantilever arm secured to the other end of the anchor arm and projecting inwardly therefrom from the pier; and

b. a quadrilateral dummy panel on the cantilever arm and including:

1. a top dummy chord on the other end of the cantilever arm for providing a top predetermined panel point to panel point length;

2. restraining means associated with the cantilever arm and the top dummy chord for preventing any change in the top predetermined panel point to panel point length;

3. a bottom dummy chord on the other end of the cantilever arm in spaced relation to the top dummy chord for providing a bottom predetermined panel point to panel point length;

4. spacing means associated with the other end of the lower dummy chord and the suspended span to prevent any decrease in the bottom predetermined panel point to panel point length; and

5. a pair of diagonals between the top dummy chord and the bottom dummy chord to complete the quadrilateral dummy panel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS For a better understanding of this invention, reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIG. 1 is a plan diagrammatic view of a cantilever truss bridge being erected by the improved method of the present invention;

FIG. 2 is a side elevational view of the cantilever truss bridge shown in FIG. 1 and showing in elevation a first quadrilateral dummy panel and a second quadrilateral dummy panel mounted on their associated first cantilever arm and second cantilever arm respectively, as well as the first suspended span projecting from the first quadrilateral dummy panels and the second suspended span projecting from the second quadrilateral dummy panels;

FIG. 3A is a fragmentary enlarged side elevational view of a top of a first top dummy chord associated with the first cantilever arm of the cantilever truss bridge, taken along the lines 3A3A of FIG. 2 in the direction of the arrows;

FIG. 3B is a plan view of the top dummy chord shown in FIG. 3A;

FIG. 4A is a fragmentary enlarged side elevational view of a bottom dummy chord associated with the first cantilever arm of the cantilever truss bridge, taken along the line 4A4A of FIG. 1 in the direction of the arrows;

FIG. 4B is a plan view of the bottom dummy chord shown in FIG. 4A;

FIG. 5A is a fragmentary diagrammatic side elevational view showing the position of the vertical members of the first suspended span with respect to the line of action of the second suspended span preparatory for the closing operation and the closing points;

FIG. 5B is a view similar to FIG. 5A showing the first suspended span closed with the second suspended span;

FIG. 6 is a side elevational view of the second anchor point of the bridge showing the shims utilized in conjunction with an expansion bearing mounted on the top of a concrete pier and the vertical jack;

FIG. 7 is a view similar to FIG. 5A showing alternative closing points for closing the first suspended span with the second suspended span;

FIG. 8 is a view similar to FIG. 7 showing further alternative closing points for closing the first suspended span with the second suspended span;

FIG. 9A is a diagrammatic fragmentary side elevational view showing the first suspended span closed at its bottom with the bottom of the second suspended span and the respective top chords of the first suspended span and the second suspended span spaced from each other; and

FIG. 9B is a view similar to FIG. 9A showing diagrammatically the application of vertical jacks adjacent the anchor points of the two half sections of the bridge for closing the top chords of the first suspended span with the second suspended span.

Although the principles of this invention are broadly applicable to suspended structures which join at the mid point of their span and must be closed together, this invention is particularly adapted for use in conjunction with a cantilever truss bridge, and hence it has been so illustrated and will be so described.

DETAILED DESCRIPTION With specific reference to the form of this invention illustrated in the drawings and referring particularly to FIGS. 1 and 2, a cantilever truss bridge is indicated generally by the reference numeral 10.

BRIDGE 10 This cantilever truss bridge 10 has a first half 12 (FIG. 2) provided with a first anchor arm 14 (FIG. 2) mounted at one end on a first anchor point 16 (FIG. 2) and at the other end on a first pier 18 (FIG. 2). Such first half 12 has a first cantilever arm 20 (FIG. 2) 'secured to the other end of the first anchor arm 14 and projects inwardly from the first pier 18.

A second half 12a (FIG. 2) of the cantilever truss bridge 10 is provided with a second anchor arm 14a (FIG. 2) mounted at one end on a second rear anchor point 160 (FIGS. 2,6) and on its other end on a second pier 180 (FIG. 2). Such second half 12a has a second cantilever arm 20a (FIG. 2) secured to the other end of the second anchor arm 14a and projects inwardly from the second pier 18a.

On the inner ends of the first cantilever arm 20 and the second cantilever arm 20a are mounted a pair of first quadrilateral dummy panels 22 (FIG. 2) and second quadrilateral dummy panels 22a (FIG. 2). Since such first quadrilateral dummy panels and second dummy quadrilateral panels 22a are essentially the same, only one of the first quadrilateral dummy panels 22 will be described in detail.

FIRST QUADRILATERAL DUMMY PANEL 22 As shown in FIGS. 1,2,3A and 38, each opposed first quadrilateral dummy panel 22 has an upper dummy chord UDC (U13-Ul4) between the panel points U13 and U14 to provide a first predetermined panel point to panel point length Ul3-U14 (FIGS. 1,2,3A,3B) and such upper dummy chord UDC (Ul3-Ul4) is restrained (as hereinafter explained) to prevent any change in this first top predetermined panel point to panel point length U13-U14 during the erection of the first suspended span 24 thereon. At the panel point U13 gusset plates 26 (FIGS. 3A,3B) connect upper dummy chord UDC (Ul3-U14) to upper chord UC (U12-Ul3) in spaced relation thereto. Such gusset plates 26 are also connected to diagonal D (LIZ-U13) and vertical hanger V (LB-U13).

At panel point U14, another pair of gusset plates 26 8 (FIGS. 3A,3B) connect the other end of the upper dummy chord UDC (U13-U14) in spaced relation to upper chord UC (U14-U15) and to diagonals D (Ll3-Ul4) and D (U14-L15) and vertical hanger V (LN-U14).

UPPER DUMMY CHORD UDC (U13-U14) As shown in FIGS. 3A and 3B, the upper dummy chord UDC (U13U14) has a restraining pin 28 (FIGS. 3A,3B) inserted through a pin hole 30 (FIGS. 3A,3B) in the left hand end of the upper dummy chord UDC (U13-Ul4) as viewed in FIGS. 3A-3B, which pin 28 extends on both sides of the upper dummy chord UDC (Ul3-Ul4) through slots 32 (FIGS. 3A, 3B) in gusset plates 26. When the first top predetermined panel point to panel point length Ul3-Ul4 is determined, locking plates 34 (FIGS. 3A,3B) having pin holes 36 therein are inserted over the ends of the restraining pin 28 and are secured to the gusset plates 26 as by welds, rivets, bolts and nuts or the like, not shown, to prevent any change in this first top predetermined panel point to panel point length Ul3-Ul'4 of the hereinafter tensioned upper dummy chord UDC (Ul3-Ul4).

As shown in FIG. 3A, the distance D indicates the position of pin 28 from the cantilever A-A of vertical hanger V (L13-U13); distance D the position of the pin 28 from its corresponding centerline in the second quadrilateral dummy panels 22a; and the distance D indicates the normal position of the pin 28 in the completed bridge 10 as hereinafter explained.

After the closing and swinging of the bridge 10 as hereinafter explained, the locking plates 34 are removed and the pin 28 is free to move in the slots 32 in the gusset plates 26 to accommodate expansion and contraction of the bridge 10.

LOWER DUMMY CHORD LDC (L12L13) A first pair of opposed bottom dummy chords LDC (LIZ-L13) (FIGS. 1,2,4A,4B) are mounted on the end of the first cantilever arm 20 for providing a first bottom predetermined panel point to panel point length LIZ-L13 (FIGS. 4A,4B) and are used to restrain movement of such (hereinafter compressed) dummy chords (LDC) (LIZ-L13) to prevent any decrease in this first bottom predetermined panel point to panel point length L12Ll3. It will be understood by those skilled in the art that this first bottom predetermined panel point to panel point length Ll2-Ll3 of the bottom dummy chord LDC (LIZ-L13) is greater than the first top predetermined panel point to panel point length U13-U14 of the top dummy chord UDC (U1- 3-U14) to compensate for the deflection of the first suspended span 24 during erection of such span 24 on the first quadrilateral dummy panels 22.

It will be appreciated that if such first opposed span 24 were weightless, such first suspended span 24 would project upwardly at an angle with respect to the horizontal axis of the bridge 10, but since such is not the case, the difference in length between the bottom panel point to panel point length Ll2-Ll3 of the compressed bottom dummy chord LDC (LIZ-L13) and the top predetermined panel point to panel point length U1- 3-U14 of the tensioned top dummy chord UDC (U1- 3-U14) permits an end vertical member V (L18-Ul8) (FIGS. 5A,5B) of the first suspended span 24 to lie in a truly vertical plane.

As shown in FIGS. 4A and 4B, the right hand end 40 of each lower dummy chord LDC (LIZ-L13) is provided with a half pin slot 38 (FIGS. 4A,4B) in such end face 40 so that a pin 42 (FIGS. 4A,4B) may be inserted into such half pin slot 38 and a registering half pin slot 38a (FIGS. 4A,4B) in the end face 40a of a pin bearing block 44 (FIGS. 3A,3B) mounted on the end 46 (FIGS. 3A, 3B) of lower chord LC (L13L14) so that the weight of the first suspended span 24 will keep the lower dummy chord LDC (LIZ-L13) in compression and the top dummy chord UDC (U13Ul4) in tension after the construction of such first suspended span 24.

It will be seen from FIG. 4B that the pin 42 extends beyond the half pin slots 38 and 38a and through holes 1 1 48 (FIG. 4B) in opposed pin plates 50 (FIGS. 4A,4B).

After the closing of the first suspended span 24 to the second suspended span 240 as hereinafter explained, and the swinging of the bridge 10, as hereinafter explained, the pin 42 is removed and a permanent pin 52 (FIGS. 4A,4B) extends through a hole 54 (FIGS. 4A,4B) in lower chord LC (L13-L14) and opposed slots 56 (FIGS. 4A,4B) in pin plates 50 to permantly connect the lower dummy chord LDC (LIZ-L13) to the lower chord LC (L13-L14) while still allowing for expansion and contraction of the bridge 10.

Thereafter, as shown in FIGS. 1 and 2, opposed pairs of diagonals D (L12-U13) and D (L13-Ul4) are disposed between each of the first top dummy chords UDC (U13-U14) and each of the first bottom dummy chords LDC (LIZ-L13) by means of gusset plates 26 to complete the first quadrilateral dummy panels 22. In like manner, the second quadrilateral panels 22a are completed on the left hand end, as viewed in FIGS. 1 and 2, of the second cantilever arm 20a.

Thereafter, the first suspended span 24 is built inwardly from the first quadrilateral dummy panel 22 from the panel points U14-U18) (FIGS. 1 and 2) and from panel points L13-L18 to complete the first suspended span 20. In like manner, the second suspended span 24a is completed (FIGS. 1,2) on the second quadrilateral dummy panel 22a from panel points U13 through U18 and from panel points Ll3'-L17 so that the first suspended span 24 and the second suspended span 24a are disposed in registry in the same horizontal plane as shown in FIGS. 2 and 5A with an erection clearance distance D (FIG. 5A) therebetween.

CLOSING OF THE BRIDGE l Thereafter, as shown in FIGS. A and 5B, horizontal jacks 58 (FIG. 2) may be employed to move either the first half 12 or the second half 12a of the bridge toward the other half of such bridge 10 so that the panel points U18 (on the dotted line of action) and L17 of the second half 12a register respectively with panel points U18 (on vertical member V (L18-Ul8) and L17a of such first half 12. In the case shown in FIGS. 5A,5B, the first half 12 moves from the position shown in FIG. 5A to the closed position shown in FIG. 58 where gusset plates 26 may be employed to secure the first half 12 to the second half 12a.

SWINGING OF THE BRIDGE l0 Thereafter, vertical jacks 60 (FIG. 2) are used at anchor points 16, 16a to simultaneously or individually to elevate for example, the left hand end of the first anchor arm 14 with respect to the first rear anchor point 16 or, for example, the right hand end (as viewed in FIG. 2) of the second anchor arm 14a with respect to the second anchor point 16a to eliminate the erection stresses in the first top dummy chords UDC (U1- 3-U14) and the first bottom dummy chords LDC (Ll2-L13) and also the second top dummy chords UDC (U13-U14) and the second bottom dummy chords LDC (Ll2'-Ll3') so that:

l. the locking plates 34 may be removed from the gusset plates 26 (FIGS. 3A,3B) thereby releasing the pin 28 to move in the slots 32 in the gusset plates 26; and

2. so that the pin 42 will become loose in the half pin slots 38 and 38a (FIGS. 4A,4B) thereby permitting the removal of the pin 42 and the pin bearing block 44 from the bottom dummy chords LDC (LIZ-L13) and LDC (L12-L13) so that the permanent pin 52 is free to move in the slots 56 in the pin plates 50.

As a result of the above description, it will be apparent that the'improved method of this invention:

1. eliminates conventional horizontal jacking in the dummy chords UDC (U13-U14) and UDC (U13- U14') and in the bottom dummy chords LDC (L12Ll3) and LDC (L12L13');

2. reduces the total jacking power requirements for the erection of the bridge 10; and

3. avoids the temporary removal of supports (not shown) at the first anchor point 16 and the second rear anchor point 16a.

ALTERNATIVE EMBODIMENTS It will be understood by those skilled in the art that alternatively if, for example, either:

a. the panel point U18 (FIGS. 5A,5B) on the vertical member V (LIB-U18) of the first half 12 has a first deviation (not shown) from the truely horizontal plane defined by the top of the piers 18,18a (FIG. 2); or

b. the panel point U18 on the dotted line of action in FIG. 5A of the second half 12a has a second deviation (not shown) from such truely horizontal plane; or

c. both the panel point U18 and the panel point U18 have such respective first deviation and second deviation from such truly horizontal line;

then it is possible to position one of the suspended spans 24,2441 with respect to the other suspended span 240,24 so that either:

a. the second deviation equals approximately the first deviation; or

b. the first deviation becomes approximately equal the second deviation.

This positioning operation is performed by one or both of the vertical jacks 60 shown in FIGS. 2,6 adjacent the anchor points 16,16a.

Stated another way, if the panel point U18 (FIG. SA) on the vertical member V (L18-Ul8) and the panel point U18 on the dotted line of action (FIG. 5) are not for some reason in registry with each other in the same horizontal plane, one of the jacks 60 (FIGS. 2,6) may be utilized to position the higher panel point at the same level as the other panel point.

Alternatively, as shown in FIG. 6, the jacking operation may be replaced by shims 62 mounted (prior to the closing of the bridge 10) on an expansion bearing 64 having segmental rollers 66 in contact with a fixed plate 68 resting on the top pf the pier 18a at the second rear anchor plate 16a (FIGS. 2 and 6).

Again, since the second half 12a of the bridge 10 is lighter than the first half 12 of the bridge 10, the panel points U18 and U18 and the panel points Ll7a and 60 L17 (FIG. 5A) may be brought into registry as shown in FIG. 5A by the addition of counterweights 70 (FIGS. 1 and 2) affixed to the second half 12a of the bridge 10.

FIG. 7 shows an alternative selection of closing points L18 and U18 on the vertical hanger V (L18-U18) for the half sections 12 with the closing points L18 and U18 on the dotted line of action of the second half 120.

FIG. 8 shows a further alternative selection of closing points, namely L17 and U18 on the first half with the closing points U18 and L170 of the second half respectively.

If, as shown in FIGS. 9A and 98, it is desirable to close the first half 12 with the second half 120 at the bottom panel L18 by means of a gusset 26 with the associated top panel points U18 and U18 separated by a distance D it is then relatively simple to utilize the jacks 60 adjacent the anchor points 16 and 16a to cause the upper panel points U18 and U18 to register with each other and be closed by a gusset 26 (FIG. 98).

From the above description, it will be understood that the present invention includes:

a. an improved method of erecting a bridge b.,c. improved dummy chords; for a panel 22;

d. an improved panel 22 for a bridge 10; and

e. an improved bridge 10.

METHOD It will be understood from the above description that the improved method of the present invention includes the following steps:

a. mounting first quadrilateral dummy panels 22 on the first cantilever arm 20 and including:

1. mounting a first pair of opposed top dummy chords UDC (U13U 14) on the other end of the first cantilever arm 20 for providing a first top predetermined panel point to panel point length (Ul3-U l4) and restraining the top dummy chords UDC (U13-U14) to prevent any damage in the first top predetermined panel point to panel point length (U13-Ul4);

2. mounting a first pair of opposed bottom dummy chords LDC (LIZ-L13) on the other end of the first cantilever arm 20 for providing a first bottom predetermined panel pointto panel point length (LIZ-L13) and restraining the bottom dummy chords LDC (LIZ-L13) to prevent any decrease in the first bottom predetermined panel point to panel point length (LIZ-L13);

a. the first bottom predetermined panel point to panel point length (L12-L13) being greater than the first top predetermined panel point to panel point length (U13-U14) to compensate for the deflection of a first suspended span 24 during erection thereof;

3. mounting a pair of diagonals (LIZ-U13) and D (Ll3-Ul4) between each of the first top dummy chords UDC (Ul3Ul4) and each of the first bottom dummy chords LDC (LIZ-L13) to complete the first quadrilateral dummy panels 22;

b. adding a plurality of pairs of successive opposed portions of the first suspended span 24 including floor and bracing members 72 of the first suspended span 24 for rigidity to each of the first quadrilateral dummy panels 22 to complete the first suspended span 24 so that:

l. a center vertical member V(L18U18) of the first suspended span 24 lies in a truely vertical plane;

c. mounting second quadrilateral dummy panels 22a on the second cantilever arm 20a and including:

1. mounting a second pair of opposed top dummy chords UDC (U13'U14) on the other end of the second cantilevered arm 20a for providing a second top predetermined panel point to panel point length (U13Ul4') and restraining the second pair of opposed top dummy chords UDC (Ul3-Ul4') to prevent any change in the second top predetermined panel point to panel point length (Ul3-Ul4);

2. mounting a second pair of opposed bottom dummy chords LDC (Ll2-Ll3') on the other end of the second cantilevered arm 20a for providing a second bottom predetermined panel point to panel point length (Ll2-L13') and restraining the second pair of opposed bottom dummy chords LDC (L12L13) to prevent any decrease in the second bottom predetermined panel point to panel point length (LIT-L13);

a. the second bottom predetermined panel point to panel point length (L12L13) being greater than the second top predetermined panel point to panel point length (U13Ul4') to compensate for the deflection of a second suspended span 24a during erection thereof; and

3. mounting a pair of diagonals D (L13'U14) and D(Ll2 -Ll3) between each of the second top dummy chords UDC (U13'-U14') and second bottom dummy chords LDC (L12-U13') to complete the second quadrilateral dummy panels 22a;

(1. adding a plurality of pairs of successive opposed portions of the second suspended span 2411, which is lighter in weight than the first suspended span 24 (including floor and bracing members 72 of the second suspended span 24a for rigidity) to each of the second quadrilateral dummy panels 22a to complete the second suspended span 24a so that:

l. a line of action of the center vertical member of the second suspended span 24a lies in a truly vertical plane and is spaced a predetermined clearance distance D from the center vertical member V( L18U18) of the first suspended span 24;

. moving one half 12 of the first half 12 and the second half 12a of the truss cantilevered bridge 10 toward the other half 12a of the first half 12 and the second half 12a so that the line of action of the second half 12a registers with the center vertical mem ber V( L18-U18) of the first half 12 to permit closing of the truss cantilevered bridge 10;

. securing the first half 12 to the second half 12a to close the truss cantilevered bridge 10;

. swinging the bridge 10 by simultaneously elevating the one end of the first anchor arm 14 with respect to the first anchor point 16 and the one end of the second anchor arm 14a with respect to the second anchor point 16a to eliminate the erection stresses in the first top dummy chords UDC (U13-U14) and the first bottom dummy chords LDC (Ll2-L13) and the second top dummy chords UDC (Ul3'-Ul4) and the second bottom dummy chords LDC (LIT-L13);

h. releasing the restraint from the first top dummy chords UDC (Ul3-U l4) and the first bottom dummy chords LDC (LIZ-L13) and the second top dummy chords UDC (U13-U14) and the second bottom dummy chords LDC (Ll2-L13) so that the dummy chords will not carry direct stress thereby:

l. eliminating jacking in the dummy chords during closing and swinging of said bridge 10;

2. reducing the total jacking requirements for the erection for said bridge 10; and

3. avoiding the temporary removal of supports at the first anchor point 16 and the second anchor point 16a at any stage of the erection of said bridge 10.

In addition, the method includes the additional steps a. positioning one suspended span of the first suspended span 24 (having a first top panel point U18 on the center vertical member V(L18Ul8) which first top panel point U18 has a first deviation from a truely horizontal plane extending through the top of one pier of the first pier l8 and the second pier 18a and the second suspended span 24a (having a second top panel point U18 on the line of action, which second top panel point U18 has a second deviation from the truely horizontal plane and the second deviation being greater'than the first deviation) with respect to the other suspended span of the first suspended span 24 and the second suspended span 24a so that:

l. the second deviation equals approximately the first deviation;

b. elevating the second anchor arm 14a of the second half 12a at second rear anchor point 16a to position the second suspended span 24a with respect to the first suspended span 24 so that the second deviation of the second top panel point U18 on the line of action equals approximately the first deviation of the first top panel point U18 on the center vertical member V(Ll8-U18) of the first half 12;

c. elevating the second anchor arm 14a prior to completion of the closing of the cantilevered truss bridge 10;

d. shimming the second anchor arm 14a (FIG. 6) to elevate the second anchor arm 140 at second rear anchor point 16a to position the second suspended span 2411 with respect to the first suspended span 24 so that the second deviation of the second top panel point U18 on the line of action of the second half 12a equals approximately the first deviation of the first top panel point U18 on the center vertical member V(L18U18) of the first half 12;

e. jacking the second anchor arm 14a (FIG. 2) to elevate the second anchor arm 14a at the second anchor point 16a to position the second suspended span 24a with respect to the first suspended span 24 so that the second deviation of the second top panel point U18 on the line of action of the second half 12a equals approximately the first deviation of the first top panel point U18 on the center vertical member V(L18Ul8) of the first half 12;

f. increasing the weight (FIGS. 1,2) of the second suspended span 24a at a predetermined location thereon, to position the second suspended span 240 with respect to the first suspended span 24 so that the second deviation of the second top panel point U18 on the line of action of the second half 12a equals approximately the first deviation of the first top panel point U18 on the center vertical member V(L18-U18) of the first half 12;

g. adding floor members 72 (FIGS. 1,2) to the second suspended span 24a at a predetermined location to decrease the second deviation of the second top panel point U18 on the line of action of the second half 12a;

h. counterweighting (FIGS. 1,2) the second suspended span 24a at a predetermined location to decrease the second deviation of the second top panel point U18 on the line of action of the second half 12a;

. distributing the weight (FIGS. 1,2) of the first suspended span 24 at a predetermined location to position the first suspended span 24 with respect to the second suspended span 24a so that the first deviation of the first suspended span 24 approximately equals the second deviation of the second suspension span 240;

j. securing a first top panel point U18 and a first bottom panel point L18 on the vertical center member V(L18-U18) of the first half 12 to a second top panel point U18 and a second bottom panel point L18 on the line of action of the second half 12 to close the truss cantilevered bridge 10 (FIG. 7);

k. securing a first bottom panel point L18 (FIGS. 9A,9B) on the vertical center member V(L18-Vl8) of the first half 12 to a second bottom panel point L18 on the line of action of the second half 12a;

. moving the first anchor arm 14 relative to the first anchor point 16 of the first half 12 and the second anchor arm 14a relative to the second anchor point 16a of the second half 12a to cause a first top panel point U18 (FIG. 9A) on the center vertical member V(Ll8-U18) of the first half 12 to register with a second top panel point U18 on the line of action of the second half 12a; and

m. securing the first top panel point U18 on the center vertical member V(Ll8-U18) of the first half 12 to the second top panel point U18 on the line of action of the second half 12a to complete the closing of the truss cantilevered bridge 10.

TOP DUMMY CHORD A top dummy chord UDC (U13-U14) for a half 12 of a cantilever truss bridge 10 is disclosed. The half 12 is provided with an anchor ann 14 (FIGS. 1,2) mounted at one end on an anchor point 16 and at the other end on a pier 18, and a cantilever arm 20 secured to the other end of the anchor arm 14 and projecting inwardly therefrom from the pier 18. The top dummy chord UDC (Ul3-U14) has:

a. the dummy top chord UDC (U13-U14) mounted on the other end of the cantilever arm 20 for providing a top predetermined panel point to panel point length (U13U14);

b. gusset means 26 for connecting the top dummy chord UDC (Ul3-U14) to the cantilever arm 20;

c. positioning means 31 (FIG. 38) associated with the top dummy chord UDC (U13-Ul4) and the gusset means 26 for providing the top predetermined panel point to panel point length U13-Ul4; and

d. restraining means 34 on the gusset means 26 for locking the positioning means 31 to prevent any change in the first top predetermined panel point to panel point length (U'13-U14) when the dummy top chord UDC (U13U]l4) is tensioned by the ad dition thereto of a first suspended span 24.

The positioning means 34 includes:

a. the gusset means 26 provided with slots 32; and

b. a pin 28 extending through the top dummy chord UDC (Ull3-U14) and the slots 32 in the gusset means 26.

The restraining means 34 includes a plate 34 provided with a locking hole 36 adapted to receive the pin 28.

BOTTOM DUMMY CHORD A bottom dummy chord LDC (LIZ-L13) for a half 12 of a cantilever truss bridge is disclosed. The half 12 is provided with an anchor arm 14 mounted at one end on an anchor point 16 and at the other end on a pier l8, and a cantilever arm 20 secured to the other end of the anchor arm 14 and projecting inwardly therefrom from the pier 18. The bottom dummy chord has:

a. the bottom dummy chord LDC (LIZ-L13) mounted on the other end of the cantilever arm 20 for providing a bottom predetermined panel point to panel point length (LIZ-L13);

b. gusset means 26 for connecting the bottom dummy chord LDC (L12-L13) to the cantilever arm 20; and

c. spacing means 41 disposed between the other end of the lower dummy chord LDC (Ll2-Ll3) and a suspended span 24,

l. the spacing means being adapted to maintain the first bottom predetermined panel point to panel point length (L12Ll3) when the bottom dummy chord LDC (LIZ-L13) is compressed by the weight of the suspended span 24.

The other end of the bottom dummy chord LDC (LIZ-L13) and the suspended span 24 are provided with registering half pin slots 38,380. The spacing means 41 includes a pin 42 in the half pin slots 38,38a provided in the other end of the lower dummy chord LDC (L12-L13) and the suspended span 24.

The lower dummy chord LDC (LIZ-L13) has expansion means 47 mounted on the other end of the lower dummy chord LDC (Ll2-L13) and the suspended span 24 to permit expansion and contraction of the bridge 10 after closing the swinging of the bridge 10.

The expansion means 47 includes a plate 50 mounted on the other end of the lower dummy chord LDC (L12L13) and the suspended span 24 and provided with a slot 56; and a pin 52 extending through the suspended span 24 and into the slot 56 in the plate 50.

The lower dummy chord LDC (LIZ-L13) may also have:

a. the expansion means 47 including a plate 50 mounted on the other end of the lower dummy chord LDC (LIZ-L13) and the suspended span 24 and provided with a slot 56; and

b. a pin 52 extending through the lower dummy chord LDC (LIZ-L13). and into the slot 56 in the plate 50.

QUADRILATERAL DUMMY PANEL A quadrilateral dummy panel 22 for a half 12 of a a. the quadrilateral dummy panel 22 on the cantilever arm 20 and including:

l. a top dummy chord UDC (Ul3Ul4) on the other end of the cantilever arm 20 for providing a top predetermined panel point to panel point length (Ul3-Ul4);

2. restraining means 34 associated with the cantilever arm 20 and the top dummy chord UDC (Ul- 3-U14) for preventing any change in said top predetermined panel point to panel point length (Ul3-Ul4);

3. a bottom dummy chord LDC (L12L13) on the other end of the cantilever arm 20 in spaced rela tion to the top dummy chord UDC (U13-U14) for providing a bottom predetermined panel point to panel point length (LIZ-L13);

4. spacing means 41 associated with the other end of the lower dummy chord LDC (LIZ-L13) and the suspended span 24 to prevent any decrease in the bottom predetermined panel point to panel point length (LIZ-L13); and

5. a pair of diagonals D (LIZ-U13) and D( L13-U14) between the top dummy chord UDC (U13-U14) and the bottom dummy chord LDC (LIZ-L13) to complete the quadrilateral dummy panel 22.

HALF BRIDGE A combination is disclosed having: a. a half 12 of a cantilever truss bridge 10 having:

1. an anchor arm 14 mounted at one end on an anchor point 16 and at the other end on a pier 18;

2. a cantilever arm 20 secured to the other end of the anchor arm 14 and projecting inwardly therefrom from first pier 18; and

b. a quadrilateral dummy panel 22 on the cantilever arm 20 and including:

1. a top dummy chord UDC (U13U14) on the other end of the cantilever arm 20 for providing a top predetermined panel point to panel point length (U13U14);

2. restraining means 34 associated with the first cantilever arm 20 and the top dummy chord UDC (U13-U14) for preventing any change in the top predetermined panel point to panel point length (U13-U14);

3. a bottom dummy chord LDC (LIZ-L13) on the other end of the cantilever arm 20 in spaced relation to the top dummy chord UDC (U13-U14) for providing a bottom predetermined panel point to panel point length (LIZ-L13);

4. spacing means 41 associated with the other end of the lower dummy chord LDC (LIZ-L13) and the suspended span 24 to prevent any decrease in the first bottom predetermined panel point to panel point length (LIZ-L13); and

5. a pair of diagonals D (LIZ-U13) and D (Ll3-U14) between the top dummy chord UDC (U13U14) and the bottom dummy chord LDC (LIZ-L13) to complete the quadrilateral dummy panel 22.

SUMMARY OF THE ACHIEVEMENTS OF THE OBJECTS OF THE INVENTION It will be understood from the above discussion of the invention that an improved method of erecting a cantilevered truss bridge an improved half bridge 12,12a; an improved quadrilateral dummy panel 22,22a for the bridge 10; and improved top dummy chords UDC (U13-Ul4), UDC (Ll3'-Ul4') and bottom dummy chords LDC (LIZ-L13) LDC (Ll2-Ll3) for the panels 22,22a have been provided which:

a. eliminate any deflection of a first suspended span 24 and a second suspended span 240 as each is cantilevered from opposed first cantilevered arm and second cantilevered arm 20a respectively;

b. eliminate jacking in the truss chords UDC (Ul- 3-Ul4), UDC (U13-Ul4'), and LDC (LIZ-L13), LDC (Ll2'Ll3); and

c. reduce the jacking requirement for closing the span to about one-fifth of that used in conventional methods.

While in accordance with the patent statutes, preferred and alternative embodiments of this invention have been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. A method of erecting a cantilever truss bridge having a first half provided with a first anchor arm mounted at one end on a first anchor point and at the other end on a first pier, and a first cantilever arm secured to said other end of said first anchor arm and projecting inwardly therefrom from said first pier; and a second half provided with a second anchor arm mounted at one end on a second anchor point and on the other end on a second pier, and a second cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said second pier, said method including the steps of:

a. mounting first quadrilateral dummy panels on said first cantilever arm and including:

2. mounting a first pair of opposed top dummy chords on said other end of said first cantilever arm for providing a first top predetermined panel point to panel point length and restraining said first pair of opposed top dummy chords to prevent any change in said first top predetermined panel point to panel point length;

2. mounting a first pair of opposed bottom dummy chords on said other end of said first cantilever arm for providing a first bottom predetermined panel point to panel point length and restraining said first pair of opposed bottom dummy chords to prevent any decrease in said first bottom predetermined panel point to panel point length;

a. said first bottom predetermined panel point to panel point length being greater than said first top predetermined panel point to panel point length to compensate for the deflection of a first suspended span during erection thereof;

3. mounting a pair of diagonals between each of said first top dummy chords and each of said first bottom dummy chords to complete said first quadrilateral dummy panels;

b. adding a plurality of pairs of successive opposed portions of said first suspended span (including floor and bracing members of said first suspended span) for rigidity to each of said first quadrilateral dummy panels to complete said first suspended span so that:

l. a center vertical member of said first suspended span lies in a truly vertical plane;

c. mounting second quadrilateral dummy panels on said second cantilever arm and including:

1. mounting a second pair of opposed top dummy chords on said other end of said second cantilvered arm for providing a second top predetermined panel point to panel point length and restraining said second pair of opposed top dummy chords to prevent any change in said second top predetermined panel point to panel point length;

2. mounting a second pair of opposed bottom dummy chords on said other end of said second cantilevered arm for providing a second bottom predetermined panel point to panel point length and restraining said second pair of opposed bottom dummy chords to prevent any decrease in said second bottom predetermined panel point to panel point length;

a. said second bottom predetermined panel point to panel point length being greater than said second top predetermined panel point to panel point length to compensate for the deflection of a second suspended span during erection thereof; and

3. mounting a pair of diagonals between each of said second top dummy chords and said second bottom dummy chords to complete said second quadrilateral dummy panels;

(1. adding a plurality of pairs of successive opposed portions of said second suspended span, which is lighter in weight than said first suspended span (including floor and bracing members of said second suspended span for rigidity) to each of said second quadrilateral dummy panels to complete said second suspended span so that:

l. a line of action of said center vertical member of said second suspended span lies in a truly vertical plane; and is spaced at predetermined clearance distance from said center vertical member of said first suspended span;

e. moving one half of said first half and said second half of said truss cantilevered bridge toward the other half of said first half and said second half so that said line of action of said second half registers with said center vertical member of said first half to permit closing of said truss cantilvered bridge;

f. securing said first half to said second half to close said truss cantilevered bridge;

g. swinging said bridge by simultaneously elevating said one end of said first anchor arm with respect to said first rear anchor point and said one end of said second anchor arm with respect to said second rear anchor point to eliminate the erection stresses in said first top dummy chords and said first bottom dummy chords and said second top dummy chords and said second bottom dummy chords; and

h. releasing the restraint from said first top dummy chords and said first bottom dummy chords and said second top dummy chords and said second bottom dummy chords so that said dummy chords -will not carry direct stress thereby;

l. eliminating jacking in said dummy chords during closing and swinging of said bridge;

2. reducing the total jacking requirements for the erection for said bridge; and

3. avoiding the temporary removal of supports at said first anchor point and said second anchor point at any stage of the erection of said bridge.

2. The method recited in claim 1 including the step a. positioning one suspended span of said first suspended span (having a first top panel point on said center vertical member, which first top panel point has a first deviation from a truely horizontal plane extending through the top of one of said first pier and said second pier) and said second suspended span (having a second top panel point on said line of action, which second top panel point has a second deviation from said truely horizontal plane and said second deviation being greater than said first deviation) with respect to the other suspended span of said first suspended span and said second suspended span so that:

1. said second deviation equals approximately said first deviation.

3. The method recited in claim 2 including the step a. elevating said second anchor arm of said second half at second rear anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action equals approximately said first deviation of said first top panel point on said center vertical member of said first half.

4. The method recited in claim 3 including the step a. elevating said second anchor arm prior to comple* tion of said closing of said cantilevered truss bridge. 5. The method recited in claim 3 including the step of:

a. shimming said second anchor arm to elevate said second anchor arm at second rear anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action of said second half equals approximately said first deviation of said first top panel point on said center vertical member of said first half.

6. The method recited in claim 3 including the step a. jacking said second anchor arm to elevate said sec-.

ond anchor arm at said second anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of said first suspended span so that said second deviation of said second top panel point on said line of action of said second half equals approximately said first deviation of said first top panel point on said center vertical member of said first half.

8. The method recited in claim 7 including the step a. adding floor members to said second suspended span at a predetermined location to decrease said second deviation of said second top panel point on said line of action of said second half.

9. The method recited in claim 7 including the steps a. counterweighting said second suspended span at a predetermined location to decrease said second deviation. of said second top panel point on said line of .action of said second half.

10. The method recited in claim 7 including the step a. distributing the weight of said first suspended span at a predetermined location to position said first suspended span with respect to said second sus pended span so said first deviation of said first suspended span approximately equals the second deviation of said second suspended span.

11. The method recited in claim 1 including the step a. securing a first top panel point and a first bottom panel point on said vertical member of said first half to said second top panel point and a second bottom panel point on said line of action of said second half to close said truss cantilevered bridge.

} The method recited in claim 1 including the steps of:

a. securing a first bottom panel point on said vertical center member of said first half to a second bottom panel point on said line of action of said second half;

b. moving said first anchor arm relative to said first anchor point of said first half and said second anchor arm relative to said second anchor point of said second half to cause a first top panel point on said center vertical member of said first half to register with a second top panel point on said line of action of said second half; and

. securing said first top panel point on said center vertical member of said first half to said second top panel point on said line of action of said second half to complete the closing of said truss cantilevered bridge.

13. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said first pier;

a. a dummy top chord mounted on said other end of said cantilever arm for providing a top predetermined panel point to panel point length;

b. gusset means for connecting said top dummy chord to said cantilever arm;

0. positioning means associated with said top dummy chord and said gusset means for providing said top predetermined panel point to panel point length; and

d. restraining means on said gusset means for locking said positioning means to prevent any change in said top predetermined panel point to panel point length when said dummy top chord is tensioned by the addition thereto of a suspended span.

14. The top dummy chord recited in claim 13 wherein said positioning means includes:

a. said gusset means provided with slots; and

b. a pin extending through said top dummy chord and said slots in said gusset means.

15. The top dummy chord recited in claim 14 wherein said restraining means includes a plate provided with a locking hole adapted to receive said pin.

16. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier;

a. a bottom dummy chord mounted on said other end of said cantilever arm for providing a bottom predetermined panel point to panel point length;

b. gusset means for connecting said bottom dummy chord to said cantilever arm; and

c. spacing means disposed between the other end of said lower dummy chord and a suspended span,

1. said spacing means being adapted to maintain said bottom predetermined panel point to panel point length when said bottom dummy chord is compressed by the weight of said suspended span.

17. The bottom dummy chord recited in claim 16 wherein:

a. said other end of said bottom dummy chord and said suspended span are provided with registering half pin slots;

b. said spacing means includes a pin in said half pin slots provided in said other end of said lower dummy chord and said suspended span.

18. The lower dummy chord recited in claim 16 and having:

a. expansion means mounted on said other end of said lower dummy chord and said suspended span to permit expansion and contraction of said bridge after closing and swinging of said bridge.

19. The lower dummy chord recited in claim 18 wherein:

a. said expansion means includes a plate mounted on said other end of said lower dummy chord and said suspended span and provided with a slot; and

b. a pin extending through said suspended span and into said slot in said plate.

20. The lower dummy chord recited in claim 18 wherein:

a. said expansion means includes a plate mounted on said other end of said lower dummy chord and said suspended span and provided with a slot; and

b. a pin extending through said lower dummy chord and into said slot in said plate.

21. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a centilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier;

a. a quadrilateral dummy panel on said cantilever arm and including:

1. a top dummy chord on said other end of said cantilever arm for providing a first top predetermined panel point to panel point length;

2. restraining means associated with said first cantilever arm and said top dummy chord for preventing any change in said top predetermined panel point to panel point length;

3. a bottom dummy chord on said other end of said cantilever arm in spaced relation to said top dummy chord for providing a bottom predetermined panel point to panel point length;

4. spacing means associated with the other end of said lower dummy chord and said suspended span to prevent any decrease in said bottom predetermined panel point to panel point length; and

5. a pair of diagonals between said top dummy chord and said bottom dummy chord to complete said quadrilateral dummy panel.

22. In combination:

a. a half of a cantilever truss bridge having:

1. an anchor arm mounted at one end on an anchor point and at the other end on a pier;

2. a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier; and

b. a quadrilateral dummy panel on said cantilever arm and including:

1. a top dummy chord on said other end of said cantilever arm for providing a top predetermined panel point to panel point length;

2. restraining means associated with said cantilever arm and said top dummy chord for preventing any change in said top predetermined panel point to panel point length;

3. a bottom dummy chord on said other end of said cantilever arm in spaced relation to said top dummy chord for providing a bottom predetermined panel point to panel point length; and

4. spacing means associated with the other end of said lower dummy chord and said suspended span to prevent any decrease in said bottom predetermined panel point to panel point length; and

5. a pair of diagonals between said top dummy chord and said bottom dummy chord to complete said quadrilateral dummy panel.

a v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3, 833,959 Dated September 10 1974 inventor) William K. McGrath It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 47, "om".should read on Column 10,

line 11, "cantilever" should read centerline Column 12, line 54, pf" should read of Column 13, line 14,

"D "'should read ;D J-; line 37, "damage" should read change Column l4, line 29, "L13" should read U13" line 31, "'Ul3 should read L13 Column 19, claim 1, line 45, "2.", should read 1.

Signed and sealed this llth day of February 1975.

(SEAL) Attesti v C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Att'esting Officer and Trademarks FORM F d-1050 (O-69) USCOMM-DC 60376-P69 U45, GOVERNMENT PRINTING OFFICE: a 9 93 O 

1. A method of erecting a cantilever truss bridge having a first half provided with a first anchor arm mounted at one end on a first anchor point and at the other end on a first pier, and a first cantilever arm secured to said other end of said first anchor arm and projecting inwardly therefrom from said first pier; and a second half provided with a second anchor arm mounted at one end on a second anchor point and on the other end on a second pier, and a second cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said second pier, said method including the steps of: a. mounting first quadrilateral dummy panels on said first cantilever arm and including:
 2. mounting a first pair of opposed top dummy chords on said other end of said first cantilever arm for providing a first top predetermined panel point to panel point length and restraining said first pair of opposed top dummy chords to prevent any change in said first top predetermined panel point to panel point length;
 2. mounting a first pair of opposed bottom dummy chords on said other end of said first cantilever arm for providing a first bottom predetermined panel point to panel point length and restraining said first pair of opposed bottom dummy chords to prevent any decrease in said first bottom predetermined panel point to panel point length; a. said first bottom predetermined panel point to panel point length being greater than said first top predetermined panel point to panel point length to compensate for the deflection of a first suspended span during erection thereof;
 3. mounting a pair of diagonals between each of said first top dummy chords and each of said first bottom dummy chords to complete said first quadrilateral dummy panels; b. adding a plurality of pairs of successive opposed portions of said first suspended span (including floor and bracing members of said first suspended span) for rigidity to each of said first quadrilateral dummy panels to complete said first suspended span so that:
 1. a center vertical member of said first suspended spAn lies in a truly vertical plane; c. mounting second quadrilateral dummy panels on said second cantilever arm and including:
 1. mounting a second pair of opposed top dummy chords on said other end of said second cantilvered arm for providing a second top predetermined panel point to panel point length and restraining said second pair of opposed top dummy chords to prevent any change in said second top predetermined panel point to panel point length;
 2. mounting a second pair of opposed bottom dummy chords on said other end of said second cantilevered arm for providing a second bottom predetermined panel point to panel point length and restraining said second pair of opposed bottom dummy chords to prevent any decrease in said second bottom predetermined panel point to panel point length; a. said second bottom predetermined panel point to panel point length being greater than said second top predetermined panel point to panel point length to compensate for the deflection of a second suspended span during erection thereof; and
 3. mounting a pair of diagonals between each of said second top dummy chords and said second bottom dummy chords to complete said second quadrilateral dummy panels; d. adding a plurality of pairs of successive opposed portions of said second suspended span, which is lighter in weight than said first suspended span (including floor and bracing members of said second suspended span for rigidity) to each of said second quadrilateral dummy panels to complete said second suspended span so that:
 1. a line of action of said center vertical member of said second suspended span lies in a truly vertical plane; and is spaced a predetermined clearance distance from said center vertical member of said first suspended span; e. moving one half of said first half and said second half of said truss cantilevered bridge toward the other half of said first half and said second half so that said line of action of said second half registers with said center vertical member of said first half to permit closing of said truss cantilvered bridge; f. securing said first half to said second half to close said truss cantilevered bridge; g. swinging said bridge by simultaneously elevating said one end of said first anchor arm with respect to said first rear anchor point and said one end of said second anchor arm with respect to said second rear anchor point to eliminate the erection stresses in said first top dummy chords and said first bottom dummy chords and said second top dummy chords and said second bottom dummy chords; and h. releasing the restraint from said first top dummy chords and said first bottom dummy chords and said second top dummy chords and said second bottom dummy chords so that said dummy chords will not carry direct stress thereby;
 1. eliminating jacking in said dummy chords during closing and swinging of said bridge;
 2. reducing the total jacking requirements for the erection for said bridge; and
 3. avoiding the temporary removal of supports at said first anchor point and said second anchor point at any stage of the erection of said bridge.
 2. The method recited in claim 1 including the step of: a. positioning one suspended span of said first suspended span (having a first top panel point on said center vertical member, which first top panel point has a first deviation from a truely horizontal plane extending through the top of one of said first pier and said second pier) and said second suspended span (having a second top panel point on said line of action, which second top panel point has a second deviation from said truely horizontal plane and said second deviation being greater than said first deviation) with respect to the other suspended span of said first suspended span and said second suspended span so that:
 2. restraining means associated with said first cantilever arm and said top dummy chord for preventing any change in said top predetermined panel point to panel point length;
 2. restraining means associated with said cantilever arm and said top dummy chord for preventing any change in said top predetermined panel point to panel point length;
 2. mounting a first pair of opposed top dummy chords on said other end of said first cantilever arm for providing a first top predetermined panel point to panel point length and restraining said first pair of opposed top dummy chords to prevent any change in said first top predetermined panel point to panel point length;
 2. mounting a first pair of opposed bottom dummy chords on said other end of said first cantilever arm for providing a first bottom predetermined panel point to panel point length and restraining said first pair of opposed bottom dummy chords to prevent any decrease in said first bottom predetermined panel point to panel point length; a. said first bottom predetermined panel point to panel point length being greater than said first top predetermined panel point to panel point length to compensate for the deflection of a first suspended span during erection thereof;
 2. mounting a second pair of opposed bottom dummy chords on said other end of said second cantilevered arm for providing a second bottom predetermined panel point to panel point length and restraining said second pair of opposed bottom dummy chords to prevent any decrease in said second bottom predetermined panel point to panel point length; a. said second bottom predetermined panel point to panel point length being greater than said second top predetermined panel point to panel point length to compensate for the deflection of a second suspended span during erection thereof; and
 2. reducing the total jacking requirements for the erection for said bridge; and
 2. a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier; and b. a quadrilateral dummy panel on said cantilever arm and including:
 3. avoiding the temporary removal of supports at said first anchor point and said second anchor point at any stage of the erection of said bridge.
 3. mounting a pair of diagonals between each of said second top dummy chords and said second bottom dummy chords to complete said second quadrilateral dummy panels; d. adding a plurality of pairs of successive opposed portions of said second suspended span, which is lighter in weight than said first suspended span (including floor and bracing members of said second suspended span for rigidity) to each of said second quadrilateral dummy panels to complete said second suspended span so that:
 3. mounting a pair of diagonals between each of said first top dummy chords and each of said first bottom dummy chords to complete said first quadrilateral dummy panels; b. adding a plurality of pairs of successive opposed portions of said first suspended span (including floor and bracing members of said first suspended span) for rigidity to each of said first quadrilateral dummy panels to complete said first suspended span so that:
 3. a bottom dummy chord on said other end of said cantilever arm in spaced relation to said top dummy chord for providing a bottom predetermined panel point to panel point length; and
 3. The method recited in claim 2 including the step of: a. elevating said second anchor arm of said second half at second rear anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action equals approximately said first deviation of said first top panel point on said center vertical member of said first half.
 3. a bottom dummy chord on said other end of said cantilever arm in spaced relation to said top dummy chord for providing a bottom predetermined panel point to panel point length; Pg,46
 4. spacing means associated with the other end of said lower dummy chord and said suspended span to prevent any decrease in said bottom predetermined panel point to panel point length; and
 4. spacing means associated with the other end of said lower dummy chord and said suspended span to prevent any decrease in said bottom predetermined panel point to panel point length; and
 4. The method recited in claim 3 including the step of: a. elevating said second anchor arm prior to completion of said closing of said cantilevered truss bridge.
 5. The method recited in claim 3 including the step of: a. shimming said second anchor arm to elevate said second anchor arm at second rear anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action of said second half equals approximately said first deviation of said first top panel point on said center vertical member of said first half.
 5. a pair of diagonals between said top dummy chord and said bottom dummy chord to complete said quadrilateral dummy panel.
 5. a pair of diagonals between said top dummy chord and said bottom dummy chord to complete said quadrilateral dummy panel.
 6. The method recited in claim 3 including the step of: a. jacking said second anchor arm to elevate said second anchor arm at said second anchor point to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action of said second half equals approximately said first deviation of said first top panel point on said center vertical member of said first half.
 7. The method recited in claim 2 including the step of: a. increasing the weight of said second suspended span at a predetermined location thereon, to position said second suspended span with respect to said first suspended span so that said second deviation of said second top panel point on said line of action of said second half equals approximately said first deviation of said first top panel point on said center vertical member of said first half.
 8. The method recited in claim 7 including the step of: a. adding floor members to said second suspended span at a predetermined location to decrease said second deviation of said second top panel point on said line of action of said second half.
 9. The method recited in claim 7 including the steps of: a. counterweighting said second suspended span at a predetermined location to decrease said second deviation of said second top panel point on said line of action of said second half.
 10. The method recited in claim 7 including the step of: a. distributing the weight of said first suspended span at a predetermined location to position said first suspended span with respect to said second suspended span so said first deviation of said first suspended span approximately equals the second deviation of said second suspended span.
 11. The method recited in claim 1 including the step of: a. securing a first top panel point and a first bottom panel point on said vertical member of said first half to said second top panel point and a second bottom panel point on said line of action of said second half to close said truss cantilevered bridge.
 12. The method recited in claim 1 including the steps of: a. securing a first bottom panel point on said vertical center member of said first half to a second bottom panel point on said line of action of said second half; b. moving said first anchor arm relative to said first anchor point of said first half and said second anchor arm relative to said second anchor point of said second half to cause a first top panel point on said center vertical member of said first half to register with a second top panel point on said line of action of said second half; and c. securing said first top panel point on said center vertical member of said first half to said second top panel point on said line of action of said second half to complete the closing of said truss cantilevered bridge.
 13. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end On an anchor point and at the other end on a pier, and a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said first pier; a. a dummy top chord mounted on said other end of said cantilever arm for providing a top predetermined panel point to panel point length; b. gusset means for connecting said top dummy chord to said cantilever arm; c. positioning means associated with said top dummy chord and said gusset means for providing said top predetermined panel point to panel point length; and d. restraining means on said gusset means for locking said positioning means to prevent any change in said top predetermined panel point to panel point length when said dummy top chord is tensioned by the addition thereto of a suspended span.
 14. The top dummy chord recited in claim 13 wherein said positioning means includes: a. said gusset means provided with slots; and b. a pin extending through said top dummy chord and said slots in said gusset means.
 15. The top dummy chord recited in claim 14 wherein said restraining means includes a plate provided with a locking hole adapted to receive said pin.
 16. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a cantilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier; a. a bottom dummy chord mounted on said other end of said cantilever arm for providing a bottom predetermined panel point to panel point length; b. gusset means for connecting said bottom dummy chord to said cantilever arm; and c. spacing means disposed between the other end of said lower dummy chord and a suspended span,
 17. The bottom dummy chord recited in claim 16 wherein: a. said other end of said bottom dummy chord and said suspended span are provided with registering half pin slots; b. said spacing means includes a pin in said half pin slots provided in said other end of said lower dummy chord and said suspended span.
 18. The lower dummy chord recited in claim 16 and having: a. expansion means mounted on said other end of said lower dummy chord and said suspended span to permit expansion and contraction of said bridge after closing and swinging of said bridge.
 19. The lower dummy chord recited in claim 18 wherein: a. said expansion means includes a plate mounted on said other end of said lower dummy chord and said suspended span and provided with a slot; and b. a pin extending through said suspended span and into said slot in said plate.
 20. The lower dummy chord recited in claim 18 wherein: a. said expansion means includes a plate mounted on said other end of said lower dummy chord and said suspended span and provided with a slot; and b. a pin extending through said lower dummy chord and into said slot in said plate.
 21. For a half of a cantilever truss bridge, said half being provided with an anchor arm mounted at one end on an anchor point and at the other end on a pier, and a centilever arm secured to said other end of said anchor arm and projecting inwardly therefrom from said pier; a. a quadrilateral dummy panel on said cantilever arm and including:
 22. In combination: a. a half of a cantilever truss bridge having: 